Even before shots were fired at Fort Sumter, slaves recognized that their bondage was at the root of the war, and they began running to the Union army. By the war's end, nearly half a million had taken refuge behind Union lines in improvised "contraband camps". These were crowded and dangerous places, with conditions approaching those of a humanitarian crisis, yet families and individuals took unimaginable risks to reach them, and they became the first places where many Northerners would come to know former slaves en masse. Drawing on records of the Union and Confederate armies, the letters and diaries of soldiers, transcribed testimonies of former slaves, and more, Manning sweeps us along, from the contraband camps, sharing insight and stories of individuals and armies on the move, to debates in the halls of Congress. The alliances between former slaves and Union soldiers which were warily begun in the contraband camps would forge a dramatically new but highly imperfect alliance between the government and the African Americans. That alliance would outlast the war, and help destroy slavery and ward off the very acute and surprisingly tenacious danger of re-enslavement. It also raised, for the first time, humanitarian questions about refugees in wartime and legal questions about civil and military authority with which we still wrestle, as well as redefined American citizenship, to the benefit but also to the lasting cost of African Americans. --